1. Field of the Invention
The present invention relates to a method and apparatus for applying a liquid material, such as adhesive, to an object of application through ejection, and more particularly to a method and apparatus for controlling the distance between and the positions of the object of application and a liquid material ejection hole with high accuracy (on the order of 10μ).
2. Related Background Art
Conventionally, in replacing the liquid material, the lower end (distal end) of a needle (application nozzle) mounted to a syringe filled with a liquid material is caused to abut a reference plate to effect positioning in the Z-direction (syringe axis direction), and the syringe and the needle are fixed to the ascent/descent drive system of an apparatus. That is, the reference plate surface constitutes the positional reference for the distal end of the needle.
It is to be noted that a needle having a small diameter will be deflected when caused to abut the reference plate and will be restored to the former state when separated from the reference plate and there is no load (that is, when the needle is in the air). As a result, with such a needle, positional deviation of the distal end of the needle in the X-, Y-, and Z-directions is involved.
Examples of the techniques regarding liquid material application are disclosed in the following publications: Japanese Patent Application Laid-Open No. 2003-1165, Japanese Patent Application Laid-Open No. 2000-317373, Japanese Patent Application Laid-Open No. 2001-87693, Japanese Patent Application Laid-Open No. 9-99268, and Japanese Patent Application Laid-Open No. 2001-291999.
Japanese Patent Application Laid-Open No. 2003-1165 discloses a construction in which an abutment terminal provided on the syringe side is caused to abut the object of application, thereby maintaining a fixed distance between the liquid material ejection hole and the reference plate.
However, since the distance between the liquid material ejection hole and the reference plate is determined by the dimensional accuracy (parts accuracy) of the abutment terminal, the syringe, and the needle with the liquid material ejection hole, the construction is not suitable for an apparatus in which it is necessary to control the distance between the liquid material ejection hole and the reference plate on the order of microns.
Japanese Patent Application Laid-Open No. 2000-317373, Japanese Patent Application Laid-Open No. 2001-87693, Japanese Patent Application Laid-Open No. 9-99268, and Japanese Patent Application Laid-Open No. 2001-291999 disclose a construction in which, in applying liquid material, the distance between the reference plate and the distal end of the needle is measured by a non-contact distance sensor.
It is to be noted, however, that the non-contact distance sensor is mounted to the syringe and a needle holding member, and the distance between the distal end of the needle and the reference plate is measured on the assumption that the distal end of the needle is always at the same position. Thus, if the position of the distal end of the needle (in the Z-direction) at the time of replacement differs from that at the time of application (when there is no load), no correction (detection) of this difference is possible.
Further, in the case of an apparatus for performing wire bonding or liquid application between IC lead terminals or to a narrow range such as IC underfill, or a high-density place, a high level of accuracy in the X-, Y-, and Z-directions of the liquid material ejection hole is required, and the distance between the ejection hole and the application surface, or the dimension for avoiding interference with the component, has to be controlled on the order of 10 microns. As a result, measures must also be taken against needle bending.